Array Operators

Table 15-8. Array Operators

Example	Name	Result
$a + $b	Union	Union of $a and $b.
$a == $b	Equality	`TRUE` if $a and $b have the same key/value pairs.
$a === $b	Identity	`TRUE` if $a and $b have the same key/value pairs in the same order and of the same types.
$a != $b	Inequality	`TRUE` if $a is not equal to $b.
$a <> $b	Inequality	`TRUE` if $a is not equal to $b.
$a !== $b	Non-identity	`TRUE` if $a is not identical to $b.

The + operator appends the right handed array to the left handed, whereas duplicated keys are NOT overwritten.

<?php
$a = array("a" => "apple", "b" => "banana");
$b = array("a" => "pear", "b" => "strawberry", "c" => "cherry");

$c = $a + $b; // Union of $a and $b
echo "Union of \$a and \$b: \n";
var_dump($c);

$c = $b + $a; // Union of $b and $a
echo "Union of \$b and \$a: \n";
var_dump($c);
?>

When executed, this script will print the following:

Union of $a and $b:
array(3) {
  ["a"]=>
  string(5) "apple"
  ["b"]=>
  string(6) "banana"
  ["c"]=>
  string(6) "cherry"
}
Union of $b and $a:
array(3) {
  ["a"]=>
  string(4) "pear"
  ["b"]=>
  string(10) "strawberry"
  ["c"]=>
  string(6) "cherry"
}

Elements of arrays are equal for the comparison if they have the same key and value.

Example 15-6. Comparing arrays

<?php
$a = array("apple", "banana");
$b = array(1 => "banana", "0" => "apple");

var_dump($a == $b); // bool(true)
var_dump($a === $b); // bool(false)
?>

See also the manual sections on the Array type and Array functions.